Moiré
A false pattern of wavy bands or colour that appears when fine repeating detail in a subject interferes with the sensor's pixel grid.
In depth
Moiré occurs when the subject's frequency approaches or exceeds the sensor's sampling rate, producing a beat pattern that was never in the scene. It is most visible on fabrics, architectural screens and distant railings, and it can be reduced by slightly changing focus, focal length or camera distance — which shifts the subject's frequency relative to the grid.
Examples in practice
A presenter's fine-striped shirt shimmers with rainbow bands on video until the camera zooms slightly.